1. Technical Field
Several aspects of the present invention relate to a semiconductor device and a method of manufacturing a semiconductor device, and more particularly to a technology to manufacture a microscopic hole and a groove on a substrate.
2. Related Art
The above-mentioned method for manufacturing the semiconductor device, for example, forms an insulating film on a substrate, and forms a contact hole to the insulating film in order to electrically connect wirings. In recent years, forming a microscopic contact hole on a relatively large substrate has been sought-after. For example, a non-patent document F. Clube et al., 0.5 μm Enabling Lithography for Low-temperature Polysilicon Displays, Society for Information Display, 2003 International Symposium, Digest of Technical Papers, volume XXXIV, book I, pp. 350-353 discloses that it is possible to form a microscopic contact hole to a large substrate by using hologram exposure technology, since it forms a high-resolution pattern.
However, the microscopic contact hole has a large aspect ratio (elongated contact hole). When a metal material is filled into the contact hole, it is difficult to fill the metal material deep into the contact hole. This problem leads to a poor coverage of the metal material and deteriorates electrical characteristics, causing a connection failure and a disconnection of wiring.
In order to improve the coverage, for example, an opening of the contact hole is enlarged for easy filling. The opening is enlarged by immersing a substrate formed with the contact hole in an etching solution. An insulating film at the opening of the contact hole is removed by this method. By enlarging the opening in such a way, filling the metal material into the contact hole can be performed with ease, thereby improving the coverage.
However, as the substrate is large, etching time differs from one end of the substrate to the other end of the substrate, when the substrate is immersed in and out of the etching solution. This results in a difference in etching quantity at the opening of the contact hole. Therefore, variations occur, such as one with wide opening and one with little etching. When the metal material is filled into the contact hole, it is difficult to fill the metal material deep into the contact hole. This problem causes a difference in the coverage, allowing variations in the electrical characteristics, and leading to a problem of generating some without electrical continuity.